We conduct water quality monitoring surveys in Minamata Bay and on the waterfront of the Eco Park Minamata to analyze mercury concentration in seawater. After seawater is sampled at fixed locations in Minamata Bay and on the waterfront of the Eco Park Minamata several times a year in varying seasons, we analyze total mercury concentration and methylmercury concentration in the dissolved state in the samples.
At present, levels in Minamata Bay have been stable, with no major change observed relative to the 10-year historical average, indicating substantially lower levels of total mercury concentration in the dissolved state (0.49 ± 0.37ng/L in total mercury concentration in the dissolved state) than the environmental standard value (500 ng/L).